Electrochemical Machining (ECM)

Electrochemical Machining (ECM) is a rapid, cost-effective machining process that eliminates heat and mechanical stress. ECM is a deplating process that utilizes the principle of electrolysis. The ECM tool (cathode) is positioned close to the work piece (anode) and a low-voltage, high-amperage direct current is passed between the two via an electrolyte. Material is removed by anodic dissolution and then carried away by the electrolyte. Two-dimensional tolerances can be held to ±0.001 inches, three-dimensional tolerances can be held to ±0.002 inches, and 5 – 15 µ inch Ra surface finishes are achieved in a single pass. Barber-Nichols routinely machines turbine blisks, axisymmetric turbine nozzles, and various components with internal helical splines for the aerospace, energy, and medical equipment industries. The following features lend themselves effectively to ECM:

• Internal Shaping (a.k.a. Plunge Holes)
  • Polygon Shaped Holes
  • High Length to Diameter Ratio Holes
  • Deep Narrow Grooves
  • Internal Helical Splines
• External Shaping & Trepanning
• Surfacing of Extremely Hard, Thin, and/or Easily Deformed Work Pieces

However, Electrochemical Machining's benefits are better understood from manufacturability perspective rather than simply from a features perspective. When a component has material requirements or features that are difficult, or even impossible, to machine by traditional methods, ECM can be an enabling alternative for the following reasons:

• Elimination of Tool Deflection - Features requiring acute/obtuse cutter approach angles and features requiring high length-to-diameter cutter ratios are strong candidates for Electrochemical Machining. This is because the ECM tool does not come into direct physical contact with the workpiece and as a result, there are no deflective forces that can cause the tool track off course.
• Preservation of Surface Integrity - Because the Electrochemical Machining process is completely free of heat, the preservation of surface integrity is maximized. The use of ECM improves wear, corrosion resistance, and metal fatigue resistance by minimizing the following undesirable surface defects.
  • Plastic Deformation
  • Microcracks
  • Heat-Affected Zones and/or Recast Layers
  • Recrystallization
  • Residual Stress
• Elimination of Secondary Processes - Electrochemical Machining produces a burr-free, inspection-ready surface finish in a single pass. Therefore, secondary processes such as deburring, grinding, and hand polishing are unnecessary.
• Preservation of Dimensional Integrity - Because Electrochemical Machining is completely free of mechanical stress, plastic deformation is eliminated. Work pieces that are thin or easily deformed by mechanical stress are strong candidates for ECM.
• Unaffected by Material Hardness - Because material is removed by anodic dissolution rather than by mechanical stress, machining rates are not affected by material hardness. Electrically conductive materials can be machined at rates up to 0.33 inches (0.84 cm) / minute. The following high-strength alloys are strong candidates for ECM.
  • Inconel^® 718 & 625
  • Rene™ 95 & 41
  • Hastelloy^® C, D, & X
  • Titanium
  • 17-4, 15-5, & 13-8 PH Stainless Steel
  • Udimet^® 720
  • MAR-M™ 246 & 247
  • Waspalloy™
  • Common Stainless Steel
  • Rhenium